Compressor synchronizing system



May 11, 1937. a RQGERS AL 2,080,232

COMPRESSOR SYNCHRONIZING SYSTEM 2 Filed Oct. 15, 1935 Them Attorneg.

Patented -May 11,

:PAT -NT ,orrics y 2,080,232 comsssoa-smcrmomzmc srs'rmr mum- B, mm,Wilmington, Bet, and William S. H. Hamilton, Larchmont, N. Y., assignorsto General Electric Company, a corporation of New York Applicationctober'15, 1935, semi No. 45,028 8 Claims. (01. ecu-e) Our inventionrelates to control systems for motor-driven compressors, moreparticularly" to systems for synchronizing the controlof a plur'ality ofpneumatically connected motor-driven compressors, and has for an objectthe provision of a simple and reliable control system of this character.

' Although our invention is not limited thereto,-

it is particularly applicable to compressed-air l0 braking systems formultiple-unit trains in which each trainunit is provided with amotor-driven compressor connected'to a reservoir and with a completecontrol equipment therefor.

When a plurality of train units are coupled l5 togetherior multiple-unitoperation, thereser- .voirs on the various train units areeonnectedtogether by means of equalizer pipe sections provided with hoseconnections between theunits.

In 'such multiple-unit systems, the total compressor capacity oftenexceeds the capacity of the hose connections. particularly when the hosecounections are provided with the usual restrictions in order to preventa complete loss of pressure in,

case one or the hose connections should burst.

The limitations presented by the hose connec:

tions in the free exchange of air between the reservoirs on the separatetrain units may therefore result in a considerable difference inpressure betweenthe various reservoirs.

It has heretofore been proposed to provide synchronizingmeans forinterconnecting the compressor control equipments on the various trainunits during multiple-unit operation. Previouslyknown synchronizingsystems, however, have usualiybeen arrangedtostartandtostopallof thecompressors One well-known type of synchronizing system, for

' example, includes means ior startingall or the motor-drivencompressors substantially simul- 40 taneously when the pressure in anyone reservoir drops below a predetermined value, and means for stoppingall of the motor-driven compressors only when all of the reservoirs havebeen charged to a predetermined pressure, that is. the last reservoir toreach the predetermined pressure controls the stopping of all of themotor-driven compressors. It will be apparent that when such asynchronizing system is employed,.some of the reservoirs may be chargedbeyond the prede-v termined pressure, and the consequent operation ofthe relief valves will result in a waste of 'air and power. y While itis desirable thatall or the compressors be started substantiallysimultaneously to pre-.

vent excessive load on some of the indiv dual substantiallysimultaneously.

taneously. responsive to operation of the pressure-responsive devicetherefor, is a relay arranged to interrupt compressors, it is alsodesirable that each of the compressors shall be stopped vwhen theassociated reservoir is charged to the predetermined pressure.Accordingly, it is a further object of our invention to" provide asynchronizing system 5 for a pluralityof interconnected motor-drivencompressors which will be effective to start all of the compressormotors substantially simultaneously and which will thereafter berendered ineffective, each of the compressor motors being 10 thereaftercontrolled entirely by its separate control equipment.

In accordance with one embodiment of our invention, a plurality ofinterconnected motordriven compressors each of which is provided with 15separate pressure-responsive means for controlling the compressor motorin accordance with the pressure set up by the associated compressor, areprovided with a control systemwhich comprises synchronizing means foroperating all of the pres- 2o sure-responsive devices independently ofpressure conditions to energize all of the compressor motors when anyone of the separate pressureresponsive devices operates in response to adrop in pressure. Means are also provided whereby the synchronizingmeans is thereupon disabled to perv mit each compressor motor to becontrolled thereafter solely in accordance with the pressure set up bythe associated compressor.

any of the pressure-responsive devices upon a drop in reservoirpressure, whereby allot the com- 40 pressor motors are energizedsubstantially simul- Associated with each compressor and the energizingcircuit tor the associated magnetic 5 valve, whereby each compressormotor is thereafter controlled solely by its associatedpressureresponsive device in accordance with the pressure in theassociated reservoir. Each of the relays'is arranged to establish aholding circuit through 50 the synchronizing wire in-order to preventreenergization of the magnetic valve until all of the compressor motorshave been deenergized by the separate pressure-responsive devices.

' For a more complete understanding or our indrawing by a spring 35, incylinder 24 is subjected to the pressure in the vention, referenceshould now be had to the drawing, the single figure of which is adiagrammatic illustration of a control system embodying our invention.

Referring now to the drawing, for purposes of illustration, we haveshown our invention in one form as applied to a pair of locomotives ortrain units indicated respectively by the reference numerals and 2,although it will of course be understood that control systems embodyingour invention are applicable to any number of train units connected formultiple-unit operation. The train unit indicated by the referencenumeral is provided with a motor-driven compressor Ill arranged tocharge a reservoir through a pipe 2, the reservoir being provided withan outlet pipe l3 which may be connected to any suitable compressed-airsystem such, for example, as the system shown somewhat diagrammaticallyin Patent No. 1,493,261 issued May 6, 1924 to William S. H. Hamilton.

As shown, the compressor motor comprises an armature 4 and a fieldwinding |5 connected in series circuit relation and energizable from asupply line l6 through a trolley I! and a control switch 8. with twopairs of interlock contacts I9 and 20 and with an operating winding 2|,the energization of which is controlled by a pair of contacts 22connected in circuit therewith and arranged to be controlled by apressure-responsive device comprising apiston 23 which is movable withina cylinder 24 in accordance with the pressure in the cylinder spring 25;

In order selectively to subject the movable piston 23 either to thepressure in the reservoir II or to exhaust, we provide a magnetic valve26 which is of a well-known type and comprises a valve casing havingdividing walls arranged to form a central compartments 28 and 29respectively. As shown, theend compartment 28 is connected to exhaust bymeans of a pipe 30, the central compartment 21 is connected to thecylinder 24 by means of a pipe 3|, and the'other end compartment 29 isconnected to the reservoir by means of a pipe 32. A movable valve stem33 is provided with spaced-apart valve heads 34 and'35 and is normallybiased to the position shown in the which position the reservoir II. Itwill be apparent that when the valve stem 33 is moved to its upperposition against the biasing force of the spring 36, the valve head 35will be operated to-close the connection between the cylinder 24 and thereservoir H, and the 'valve head 34 will be operated to open theconnection between the cylinder 24 and the exhaust pipe 30. The magneticvalve 25 is provided with an operating winding 31, the energization ofwhich is controlled-by a relay 38 having a'plurality of. pairs ofcontacts 39 and 40.

meral 2 is identical with the -.:scribed, and it isbelieved that acomplete un-' -:wderstandingof our invention may now be had In addition,the control equipment for the trainunit includes a suitable source ofcontrol energy-such,-for example, as the battery 4|, and a synchronizingwire 42 the opposite ends of which are provided with coupling members43.

The arrangement of the motor-driven compressor and the control equipmenttherefor on the train unit indicated by the reference nuequipment justdefrom a description of the operation'of the sys- The control switch I8is provided.

against the biasing force of a,

compartment 21 and two end tem as a whole, during which description thesame reference numerals followed by the letter a will be used todesignate corresponding parts on the train unit 2.

In the drawing, the various devices of the control equipments are shownin the respective positions corresponding to normal pressure conditionsinthe reservoirs II and ||a.- It will be assumed now that the train unitI isthe leading unit, in which case it will be understood that thesupply of air to the braking system of the train will be controlled by abrake valve on that unit, which will tend to lower the pressure in thereservoir II more quickly than in the reservoir II a. It will further beassumed that the braking system for the train has been so operated as tocause a drop in pressure in the reservoir below the predeterminedminimum.

Upon such a decrease in pressure-in the reservoil H, the movable piston23 will be forced downward by the spring 25 to close the contacts 22 andestablish an energizing circuit for the operating winding 2| of thecontrol switch I8. This energizing circuit may be traced from thebattery 4|, through the conductors 45, 46 and 41, the contacts 22, theconductor 48 and the operating winding 2| to the ground connection 49and by way of the ground connection 44 .to the other side of thebattery. As soon as the operating winding 2| is energized, the controlswitch I8 will be closed to-energize the armature I4 and the fieldwinding l5 of the compressor motor, the energizing circuit for the motorextending from the supply line I6 through the trolley H, the conductor50, the switch l8, the conductor 5|, the motor armature l4 and the fieldwinding |5 to the ground connection 52. It will be remembered that inorder to prevent excessive load on the compressor "I, it is desirable toenergize the driving motor for the compressor Illa substantiallysimultaneously. with the driving motor for the compressor HI, andaccordingly we provide synchronizing means for energizing the compressormotor on the train unit 2 independently of the pressure 'in thereservoir Ila.

Simultaneously with the closure of the switch l8, the interlock contacts20 are closed to establish an energizing circuit for the operatingwinding 31a of the magnetic valve 26a, which circuit may be traced fromthe battery 4|a, through the conductors a and 53a, the operating winding31a, the conductor 54a, the relay contacts 39a, the conductor 55a, thesynchronizing wires 42a and 42, the conductors 55 and 56, the interlockcontacts 20, and by way of the ground connections 51 and 44a to theother side of' the battery 4|a. Upon energization of the operatingwinding 31a, the valve stem 33a of the magnetic valve 26a is operated toits upper position to connect the cylinder 24a of thepressure-responsive device to exhaust and consequently, the movablepiston 23a is forced downward by'the spring 25a to close the contacts22a and energize the operating winding 2|a of the control switch |8aindependently of the pressure in the reservoir Ila.

It will now-=be apparent that the compressors on the two train units areoperating to charge the associated reservoirs and while there will besome interchange of air between the reservoirs and Ila, it will beremembered that the restriction in the equalizer pipe is such as tocauseone of the reservoirs to be charged to the required pressure prior tothe other reservoir. As hereinbefo're mentioned, each compressor motorshould therefore be deenergized whenthe associated reservoir is chargedto the required pres-- sure and accordingly, the above describedsynchronizing means must be disabled to permit individual control of thecompressor motors.

This disablement of the synchronizing means is accomplished by therelays 38 and 38a, the

' contacts 39 and 39a of which are connected in the energizing circuitsof the magnetic valves 26 and 26a respectively. As shown, the interlockcontacts I90. which close simultaneously with the switch Illa arearranged to establish an enerway of the ground connections 51a and Ma tothe other side of the battery. The contacts 39a are thereupon opened todeenergizethe windingfl'la, and the valve stem 33a of the magnetic valve26a. is returned by the spring 36a to the position shown in the drawing,in which position the piston 23a of the pressure-responsive device isagain subjected to the pressure in the reservoir Ila and will beoperated to deenergize the winding ;2la. of the switch I8a when thepressure in the reservoir Ila reaches the desired value. Similarly, therelay 38 is energized upon operation of the switch l8 to interrupt theenergizing circuit of the operating winding 31 so as to prevent, a falseoperation of the magnetic valve 26.

lit will be apparent now that unless means are provided for maintainingthe synchronizing means in the disabled condition, the relay 3811 willbe deenergized when the interlock contacts we and a are opened upondeenergization of the switch lfla and consequently, the magnetic valve26a will be energized through the previously traced circuit 'to cause animmediate reenergization of the switch l8a. Accordingly, the contactsMia of the relay 3811. are. arranged to establish a holding circuit forthe relay, which may be traced from the battery Ma through theconductors a, 66a and 58a, the operating winding of the relay 38a, theconductor 59a, the contacts 40a, the conductor 55a, the synchronizingwires 12a and 42, the conductors 55 and 56, the interlock contacts 20and by way of the ground connections 51 and 44 a,to the other side ofthe battery. This holding circuit for therelay 38a will be interruptedonly when .the control switch i8 is opened upon the attaimnent oftherequired pressure in the reservoir Ii. I

It will be apparent now that since the separate control equipments onthe two train units are identical throughout, the operation will be.

exactly the same in case the reservoir Ha is the first to suffer adecrease in pressure and is the last to be charged to the requiredpressure.

It will also be obvious that our improved control system may be appliedto any number of train units, in which case all of the magnetic valveswould be energized through the synchronizing wire upon operation of anyof the pressureresponsive devices to energize the associated compressormotor, and all of the relays corresponding to the relays 38 and 38awould be energized to disable the'synchronizing means by interrupting'the energizing circuits for the magnetic valves, each of the relaysbeing arranged to establish a holding circuit therefor which would beinterrupted only when the last control switch is deenergized. 1

While we have shown a particular embodiment of our invention, it will beunderstood, of course, that we do not wish to be limited thereto sincemany modifications may be made and we, therefore, contemplate by theappended claims to cover any such modifications as fall within the truespirit and scope of our invention.

What we claim as new and desire to secure by Letters Patent of theUnited States is:

1. A control system for a plurality of interconnected motor-drivencompressors comprising in combination, separate means for controllingthe energization of each compressor motor in accordance with thepressure set up by the associated compressor, synchronizing meansresponsive to motor energizing operation of any one of said separatecontrol means for operating the remaining control means to energize allof the compressor motors substantially simultaneously, and meansresponsive to said operation of said control means for disabling saidsynchronizing means whereby each of said compressor motors .isthereafter controlled solely in accordance with the pressure set up bythe associated compressor.

2. A control system for a plurality of interconnected motor-drivencompressors comprising in combination, separate means for controllingthe energization of each compressor motor in accordance with thepressure set up by the associated compressor, synchronizing meansresponsive to motor energizing operation of any one of said separatecontrol means for operating the remaining control means to energize allof the compressor motors substantially simultaneously, means responsiveto said operation of said control means for disabling said synchronizingmeans compressor motors, separate means for controlling each of saidswitches in accordance with the pressure set up by the associatedcompressor, synchronizing means responsive to closure of any one of saidswitches for effecting operation of the remaining separate control meansto close all of said switches whereby all of said motors are energizedsubstantially simultaneously, and means responsive to closure of saidswitches for disabling said synchronizing means whereby each of saidswitches is thereafter controlled solely in accordance with the pressureset up by the associated compressor.

4. A control system for a plurality of interconnected motor-drivencompressors comprising in combination, aseparate control switch for eachcompressor motor, each of said switches being movable between open andclosed circuit positions for separately controlling the energization ofthe compressor motors, separate means for controlling each of saidswitches in accordance with the pressure set up by the associatedcompressors, synchronizing means" responsive to closure of any one ofsaidsyvitches for effecting operation of the said switches whereby allof said motors are energized substantially simultaneously, meansresponsive to closure of said switches for disabling said synchronizingmeans whereby each of said switches is thereafter controlled solely inaccordance with the pressure set up by the associated compressor, andmeans for maintaining said disabling means in effective position untilall of said switches have been opened by said separate control means.

5. A control system for a plurality of motordrlven compressors supplyinga plurality of connected reservoirs comprising in combination, separatemeans responsive to the pressure in each reservoir for controlling theassociated comprssor motor, synchronizingmeans responsive to operationof any of said control means on a decrease in pressure in the associatedreservoir for operating the remaining control means to energize all ofthe compressor motors substantially simultaneously, and means responsiveto said operation of said control means for rendering said synchronizingmeans inefiectivewhereby each of said compressor motors is thereafterdeenergized solely in accordance with the pressure in the associatedreservoir.

6. A control system for a plurality of motordriven compressors supplyinga plurality of connected reservoirs comprising in combination, sep aratemeans responsive to the pressure in each reservoir for controlling theassociated compressor motor, synchronizing means responsive to operationof any of said control means on a decreasecontrol means for renderingsaid synchronizing means ineffective whereby each of said compressormotors is thereafter deenergized solely in accordance with the pressurein the associated reservoir, and means for maintaining said last,-

mentioned means in a position rendering said synchronizing meansineffective until all of said compressor motors have been deenergized bysaid separate control means.

'7 A control system for a plurality of interconnected motor-drivencompressors comprising in combination, a separate switch movable betweenopen and closed circuit positions for controlling the energization ofeach compressor motor, sepa rate means for controlling each'of saidswitches in accordance with the pressure set up by the associatedcompressor, separate magnetic valve means for operating each of saidcontrol means independently of the pressure set up by the associatedcompressor, -a synchronizing wire for interconnecting the control ofsaid magnetic valve means, means responsiveto closure of any of saidswitches for energizing said magnetic valve means through saidsynchronizing wire whereby the remaining separate control means areoperated to close all of said switches substantially simultaneously,means associated with each of said switches and responsive to closurethereof for disconnecting said synchronizing wire from said valve meanswhereby each of said switches is thereafter controlled solely inaccordance with the pressure'set up by the associated compressor, andmeans for maintaining all of said last means in disconnect- I ingposition -until all of said switches have been opened by said separatecontrol means.

8. In a compressed air system employing a plurality of motor-drivencompressors, the combination of individual control means for eachcompressor, synchronizing means interconnecting said individual controlmeans for causing operation of all of said control means when'any one

